Can MRIs Diagnose ADHD?

Jean-Paul Pelissier/Reuters

In May, the Centers for Disease Control and Prevention (CDC) reported that approximately 10,000 toddlers across the country were being medicated for attention deficit hyperactivity disorder, or ADHD. Understandably, many members of the medical community did not take well to this news: The American Academy of Pediatrics' ADHD diagnosis guidelines only extend to children 4 years and older. That's because behaviors associated with ADHD, such as hyperactivity and impulsivity, are quite common in perfectly healthy toddlers. There's a reason, after all, that they call them the "terrible twos."

This is not the first time concern has arisen that ADHD might be widely misdiagnosed — and that thousands of kids are being medicated without good reason. In a CDC study of adolescent ADHD based on data from Oklahoma and South Carolina, researchers found that only approximately 33 percent of children medicated for the disorder actually met the diagnostic criteria. (In Oklahoma, it was 28.3 percent; in South Carolina, it was 39.5 percent.)

A new magnetic resonance imaging (MRI) technique, however, could one day enable doctors to make more accurate ADHD diagnoses — and, in turn, more medically sound decisions about prescribing medications — by detecting how much iron is present in the brain, according to a paper published Tuesday in the journal Radiology.

Vitria Adisetiyo, a postdoctoral research fellow at Medical University of South Carolina, in Charleston, led the study. She explains that iron is essential to normal brain function, including maintaining adequate levels of dopamine, a neurotransmitter associated with how the brain regulates pleasure and impulse, among other behaviors. Lower levels of brain iron are associated with lower levels of dopamine, she says.

There's also a link between low levels of dopamine and ADHD. Stimulants used to treat the disorder boost dopamine levels.

Adisetiyo says she and her colleagues thus wanted to explore the relationship between brain iron and ADHD.

"We're thinking, 'let's try to measure brain iron in these kids,"she says.

So the research team brain used an MRI to measure brain iron levels in 22 children and adolescents with ADHD. Twelve had never been on medication for their condition. The team also measured brain iron levels in 27 non-ADHD, non-medicated children and adolescents to act as the control group. The researchers found that ADHD patients without a history of stimulant therapy had lower iron levels. In comparison, ADHD patients with a history of stimulant therapy "had brain iron levels comparable to controls suggesting that brain iron may increase to normal levels with psychostimulant treatment," according to press release.

These findings suggest that further exploration of the brain iron-ADHD link might be promising, though Adisetiyo is the first to admit that this research is preliminary — she and her colleagues plan on conducting another, larger study to see whether they can replicate the findings. They would also follow the children and adolescents in the study group over time, to track iron-level changes before and after they start medication.

For Adisetiyo, however, the potential for diagnosing ADHD with the help of scientific measurement is exciting, as the condition is presently diagnosed with largely subjective, behavioral analysis.

"If we had an actual, physiological biomarker, especially in borderline cases — which there are many — that would be huge," she says.

Correctly diagnosing ADHD isn't just important to prevent inappropriately medicating children — a misdiagnosis could mask a serious medical problem says Susanna N. Visser, an epidemiologist with the CDC specializing in behavioral disorders.

For example, hyperactivity associated with ADHD could actually be mania or hypomania from bipolar disorder. Likewise, inattentiveness could signify depression. Other behavior or mood changes associate with ADHD could also be conditions such as sleep disorders or even some sort of trauma.

"There are many things that look like ADHD," Visser says. "It's very impt to dig down to the root of the cause of the symptoms and not call everything ADHD that looks like ADHD."